The polyphenylene ether resins are a family of engineering thermoplastics that are well known to the polymer art. These polymers may be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,257,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes for preparing polyphenylene ether resins, including graft copolymers of polyphenylene ethers with styrene type compounds, are found in Fox, U.S. Pat. No. 3,356,761; Sumitomo, U.K. Pat. No. 1,291,609; Bussink et al., U.S. Pat. Nos. 3,337,499; Blanchard et al., 3,219,626; Laakso et al., 3,342,892; Borman, 3,344,116; Hori et al., 3,384,619; Faurote et al., 3,440,217; and disclosures relating to metal based catalysts which do not include amines, are known from U.S. Pat. Nos. such as Wieden et al., 3,442,885 (copper-amidines); Nakashio et al., 3,573,257 (metal-alcoholate or -phenolate); Kobayashi et al., 3,455,880 (cobalt chelates); and the like. In the Stamatoff patents, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, an acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead dioxide, silver oxide, etc., are described in Price et al., U.S. Pat. No. 3,382,212. Cizek, U.S. Pat. No. 3,383,435 discloses polyphenylene ether-styrene resin compositions. All of the above-mentioned disclosures are incorporated herein by reference.
In the prior art, rubber-modified styrene resins have been admixed with polyphenylene ether resins to form compositions that have modified properties. The Cizek patent, U.S. Pat. Nos. 3,383,435, discloses rubber-modified styrene resin-polyphenylene ether resin compositions wherein the rubber component is of the unsaturated type such as polymers and copolymers of butadiene. The physical properties of these compositions are such that it appears that many of the properties of the styrene resins have been upgraded, while the moldability of the polyphenylene ethers is improved.
Nakashio et al. U.S. Pat. No. 3,658,945 discloses that from 0.5 to 15% by weight of an EPDM rubber modified by grafting with styrene may be used to upgrade the impact strength of polyphenylene ether resins. In Copper et al., U.S. Pat. No. 3,943,191 it is disclosed that when the highly unsaturated rubber used in compositions of the type disclosed by Cizek is replaced with EPDM rubber that has a low degree of residual unsaturation, the thermal oxidative stability and color stability are improved. The disclosures of the Nakashio et al. and Copper et al. patents are incorporated herein by reference.
It is disclosed in Haaf, U.S. Pat. No. 3,737,479 that molding resins comprised of polyphenylene ether resins and polysiloxanes are useful. These compositions are prepared by mechanical mixing and, while the compositions are useful for many purposes, they have low notched Izod impact strength. The Haaf patent is incorporated herein by reference.
It has now been found that a composition of a polyphenylene ether resin and an alkenyl aromatic resin modified with a polysiloxane in the form of small rubber-like particles is a very useful thermoplastic molding material having good ductility, good surface appearance, and good impact strength and having excellent processing characteristics and thermal oxidative stability.
It is, therefore, a primary object of this invention to provide improved compositions that are based on polyphenylene ether resin and modified alkenyl aromatic resins.
Another object of this invention is to provide molding compositions and molded articles that are based on a polyphenylene ether resin and an alkenyl aromatic resin modified with a polysiloxane in the form of small rubber-like particles and that have improved thermal oxidative stability.
Still another object of this invention is to provide molding compositions and molded articles that are based on a polyphenylene ether resin and an alkenyl aromatic resin modified with a polysiloxane in the form of small rubber-like particles and that have improved impact strength.
It is also an object of this invention to provide the above-described, improved molding compositions in reinforced and/or flame-retardant embodiments.